Hypodermic syringe



Oct. 31, 1944. a J, EVE E T 2,361,617

HYPODERMIC SYRINGE Filed May 21, 1941 inge is liable to occur.

Patented Oct. 31, 1944 Samuel James Everett, Thornton Heath, England.

ApplicationMay 21, 1941', Serial No. 394,547 In Great Britain June 1',1940 7 Claims.

When a hypodermic syringe is subjected, as sometimes happens, to rapidand substantial temperature changes, for example when the syringe isplunged intoboiling water or when a hot syringe is plunged into coldliquid, undesirable expansion orcontraction of the parts of the syr-Volumetric changes in the barrel can beavoidedby manufacturing: thisfrom a low-expansion glass, such as. the glass sold under the registeredtrade-mark Pyrex. However, the arrangement of the metal parts of thesyringe, so-that they'can readily adaptthemselves to temperaturechanges, presents a problem, particularly because low-expansion metalscorrode too'readily to allow them to be used in hypodermic syringes,whereas brass which expands and contracts considerably withtemperature-changes is a very convenient metal for the purpose. 1

One aim of the present invention, therefore, is to provide ahypodermicsyringe which is constructed so that the parts can readilyaccom modate themselves to temperature changes. This aim is achieved,according to-the invention; by providingthe syringe witha frame whichacts resiliently on the center of a front closure memher, to secure thelatter to the barrel, and reacts against the opposite end of the barrel,the frame comprising radial arms lying beyond the front closure memberand connected by tension members to an element that acts on the rear endof the barrel. Thus, the resilience in the frame ensures that, ifthere'is-a differential expansion of the parts, they remain properlyassembled and undesirable distortions and changes in stress do notoccur. Such differential expansion arises, for instance, when the barrelis=made of low-expansion glassand other parts are of brass. Theresilience incorporated in the frame then compensates for a changein thelength of the frame relatively to the barrel and the frame can bearranged so that the front closure member can expand relatively to thebarrel without any undesired effects.

The necessary resilience may be provided in any convenient manner; forexample, a resilient element canbe interposed between the frame and therear end of the barrel, but advantageously the resilience maybe providedby a flexible yoke, which incorporates the said radial arms and whichbears upon, or is integral with, the front closure member. The frame mayconsist of the yoke,- a ring bearing against the opposite end of thebarrel, and two tie rods lying in a' plane containing theaxisoftheharrel and connectingtween the plate andthebarrel;

In order that the invention may be clearly-understood andreadily carriedintoefiect, constructions in-accordance therewith will now be described;by way of example, with reference to the accompanying drawing,in-which':

Figure 1 is a sectionalelevation of a-hypodermic syringe,

Figure 2 isa plan of the syringe in Fig. 1- as viewed in the directionof the arrow II,

Figure 3 is a plan of the syringe. in Fig. 1 as viewed inthe directionofthe arrow III,

Figure 4 is-a plan of a detail of the syringe in Fig. 1.

Figure 5 is a sectional elevation of a modifiedf'orrnofhypodermicsyringe,

Figure 6 is a section on the line VI-VIin Fig. 5.

Figure 7' is a plan of one endofathird form of syringe, and

Figure 8 is a section on-.the line VIII--VIII in Fig. 7.

Referring to the syringe shown in Fig. 1, this comprises a glass barreli to which a frame serves to secure a glass front closure-member 2 aglass plate 3 being interposedbetween the barrel Land the closure member2. The latter comprises a disc 21 formed with a central nozzle lhaving afine central passage 5 which registers withacorresponding port 6 intheplate 3L The. frame comprises a resilient yoke'l' which bears uponthe front. closure member 2: and is formed with a central aperturethrough: which the nozzle 4 extends. When the syringe isin use a hollowcap, carrying. a hypodermic needle, is fitted over the nozzle 4'inthevmannerwell known in the art. The frame also includes. tie. rods 8lying in a plane passing through the. axis of the barrel and screwed at;their: endsinto tapped holes at the'ends of the'yoke-li At 'their'outerends. the tie rods pass: through? holes; ina'. ring 9 that bears againstthetremotesendxof the:baizrel l Beyond the. ring 9: thetierrods ararevthreadedto receive nuts. I 0. Thelatter which bearagainstthe ring 9 aretightened until the desired strain exists in the resilient yoke I, andthe barrel I and plate 3 are securely held between the front closuremember 2 and the ring 9. It will be seen that the ring 9 is formed witha central opening large enough to permit the insertion of a piston I Icarried by a comparatively thin piston rod I2. The piston II is formedso as to receive a piston ring [3.

To prevent the inadvertent withdrawal of the piston II from the barrelI, a readily detachable plate I4 is provided upon the ring 9. Thisplate, which is shown by itself in Fig. 4, is formed with a radial slotI5 and arcuate slots I6 and H which are tapered in the circumferentialdirection. When the detachable plate I4 is to be secured, the piston rodI2 is passed radially along the slot I5 to the centre of the plate I4which is then moved towards the barrel with the wider end of the slot Itin alignment with one of the nuts Ill. The latter will then projectthrough the slot I6 while the other nut projects through the radial slotI5 until the heads of the nuts I lie beyond the plate I4 and undercutparts ID of the nuts lie within the slots. The plate It can then beturned about the axis of the barrel so that the arcuate slots I6 and Ilpass circumferentially along the undercut parts I0 of the nuts If) tothe position shown in Fig. 3 in which the plate I4 is locked to theframe by the heads of the nuts I0 overlapping the narrow ends of theslots I6 and I1.

One way in which the syringe shown in Figures and 6 differs from that ofFig. 1 is that a metal closure member 2a is formed integrally with anozzle 4a as well as a resilient yoke la. The yoke Ia, the rods to and aring 9a provide the frame which secures the front closure mem ber 2a tothe barrel Ia. A glass disc 3a is again interposed between thesemembers. The piston I Ia in this construction is made entirely of glassand consists of a plunger of uniform cross section formed at its outerend with a thumb button 25. To prevent the plunger Ila from sliding toofreely in the barrel, friction devices 26 are arranged to bear againstthe surface of the plunger. These friction devices are small anglepieces, through which the rods 8a pass and which are secured between thering 9a and the nuts Iila carried by therods 8a.

The modification shown in Figures 7 and 8 comprises a closure member 2bwhich bears directly against the glass barrel Ib and is integral with aresilient yoke Ib forming part of a frame similar to that appearing inFig. 5 and including rods 81). The nozzle 41) in this construction iseccentrically disposed in relation to the barrel.

In a further modification the nozzle is separate from the front closuremember and is formed with a conical external surface that fits in aconical mouth formed in the port in the closure member. The nozzleprojects through an aperture in the centre of the resilient yoke and thelatter bears on a shoulder on the nozzle so as to hold the nozzle inengagement with the closure member as well as the closure member inengagement with the barrel or with the glass disc interposed between thebarrel and the closure member.

In assembling a syringe constructed as shown in the drawing, the frameis first assembled with the ring 9 or 9a and the front closure member 2.2a or 2b substantially in the relative positions they are ultimately tooccupy but with the ring slightly-more separated from the front closuremember. Then the barrel I, Ia or Ib and any glass disc 3 or 3a areinserted laterally into the frame and put in the positions they are tooccupy with respect to the ring and front closure member. Next, the nutsID or Illa are tightened so that the parts are clamped together betweenthe resilient yoke I, Ia. or 'Ib and the ring 9 or 9a. Then the pistonis inserted. Finally any plate, such as the plate I I, is secured inposition in the manner described above. The degree to which the nuts IDare tightened is such that the parts remain tight in engagement witheach other in spite of any differential expansion or contraction thatmay occur on account of temperature changes, such expansion orcontraction being accommodated by the bending of the arms of the yoke.

I claim:

1. A hypodermic syringe comprising, in combination, a barrel, a pistonslidable within said barrel, a front closure member, including a discand a nozzle extending forward from said disc, and a frame adapted tosecure said front closure member to said barrel, said frame including aresilient yoke acting substantially centrally on said front closuremember, a reaction member arranged to react against the rear end of saidbarrel and tension means extending longitudinally beside and spaced fromsaid barrel and connecting said reaction member to said yoke, the latterincluding arms radiating from said nozzle and spaced fromsaid disc.

2 A hypodermic syringe comprising, in combination, a barrel, a pistonslidable within said barrel, a front closure member comprising a discwith a projecting nozzle, a resilient yoke bearing centrally on saidclosure member to secure the latter to said barrel, a reaction memberbearing on the rear end of said barrel, and ties spaced from said barrelconnecting said reaction member and the extremities of said yoke, thelatter consisting of arms spaced from said disc and radiating from thecentre of said disc.

3. A hypodermic syringe comprising, in combination, a barrel, a pistonslidable within said barrel, a front closure member comprising a discwith a nozzle extending axially therefrom, resilient arm's extendingradially from said nozzle and spaced from said disc, a reaction memberadapted to bear upon the rear end of said barrel, and ties spaced fromsaid barrel connecting the outer ends of said resilient arms to saidreaction member.

4. A hypodermic syringe comprising, in combination, a barrel, a pistonslidable within said barrel, a front closure member comprising a discwith a nozzle extending therefrom parallel to but to one side of theaxis of said barrel, resilient arms radiating from the centre of saiddisc, a reactionmember arranged to react against the rear end of saidbarrel, and ties connecting the outer ends of said resilient arms tosaid reaction member.

5. A hypodermic syringe comprising, in combination, a barrel, a pistonslidable within said barrel, a front closure member, a central nozzle onsaid member, a yoke formed with a central aperture to receive saidnozzle and with resilient radial arms, a reaction member resting on therear edge of said barrel, and tie rods connectfront closure member tomaintain same in position with respect to said barrel, said frameincluding a ring resting on the rear edge of said barrel, and formedwith an aperture through which said piston can be removed, a pair ofdiametrically opposed radial resilient arms lying on the side of saidclosure member remote from said barrel, two tie rods connecting the endsof said arms respectively to said ring, and means for adjusting said tierods to vary the distance between said ring andhsaid ends of said arms.

7. A hypodermic syringe comprising, in combination, a barrel, a pistonassembly including a piston rod and a piston slidable in said barrel, afront closure member, a nozzle projecting forwardly from said closuremember, radial resilient arms projecting from said nozzle, a ringresting on the edge of said barrel remote from said closure member andformed with a central aperture through which said piston can pass andwith small lateral apertures, tie rods fixed to said arms and passingthrough said small apertures, heads on said tie rods bearing on the faceof said ring remote from said barrel, and a detachable plate formed witha radial slot through which said piston rod passes and with arcuateslots cooperating with said heads to hold said plate in position.

SAMUEL JAMES EVERETT.

